Abstract:

A control-mode switching device includes: a plurality of actuators (2, 6,
7) that conduct different movement; driving means (10, 11, 12, 13, 14,
15) that drive the actuators; a plurality of control levers (22a-22c)
that command operation of the driving means; a plurality of limit
switches (72a-72e) that detect arrival of the control levers to the
proximity of an end of a control range; a mode judging means (controller
23) that judges whether a priority operation mode is taken or not in
accordance with a combination of on/off conditions of the limit switches;
and a drive controlling means (controller 23) that, when it is judged by
the mode judging means that the priority operation mode is taken,
controls the driving means so that an output of selected one or more of
the driving means becomes larger than that in a normal mode or the power
ratio as compared with the other driving means becomes larger.

Claims:

1. A control-mode switching device of a construction machine, comprising:a
plurality of actuators that conduct different movement;a driving means
that respectively drives the plurality of actuators;a plurality of
control levers that command movements of the driving means;a plurality of
detecting means that respectively detect arrival of the control levers to
the proximity of ends of the control ranges of the control levers;a mode
judging means that judges whether a priority operation mode in which
output of selected one or more of the driving means becomes larger than
that in a normal mode or power ratio of the selected one or more of the
driving means as compared to other driving means becomes larger is taken
or not based on a combination of detected conditions of the detecting
means;and a drive controlling means that, when it is judged by the mode
judging means that the priority operation mode is taken, controls the
driving means so that the output of the selected one or more of the
driving means becomes larger than that in the normal mode or the power
ratio of the selected one or more of the driving means as compared to
other driving means becomes larger.

2. The control-mode switching device of a construction machine according
to claim 1, the mode judging means comprising: a storing means that
stores a plurality of priority operation modes corresponding to the
combination of the detected conditions of the detecting means; and a
selecting means that selects the priority operation mode corresponding to
the combination of the detected conditions of the detecting means from
the storing means.

3. The control-mode switching device of a construction machine according
to claim 1,wherein the actuator includes a hydraulic actuator,the driving
means includes a hydraulic circuit and a flow-rate controlling means that
controls a flow rate of the hydraulic circuit, andwhen it is judged by
the mode judging means that the priority operation mode is taken, the
drive controlling means controls the flow-rate controlling means so that
pressure oil supply that is supplied to selected one or more of the
hydraulic circuits becomes larger than pressure oil supply that is
supplied to the other hydraulic circuit.

4. The control-mode switching device of a construction machine according
to claim 1, further comprising an engine that drives the plurality of
driving means,wherein the drive controlling means increases or decreases
power of the engine.

5. The control-mode switching device of a construction machine according
to claim 1, further comprising a battery that drives the plurality of
driving means,wherein the drive controlling means increases or decreases
power of the battery.

6. The control-mode switching device of a construction machine according
to claim 1, wherein the actuator includes a hydraulic actuator,the
driving means includes a hydraulic circuit and a variable
pressure-control valve that varies pressure in the hydraulic circuit,
andwhen it is judged by the mode judging means that the priority
operation mode is taken, the drive controlling means controls the
variable pressure-control valve so that the pressure in selected one or
more of the hydraulic circuits increases.

7. The control-mode switching device of a construction machine according
to claim 1, further comprising a notifying means that allows an operator
to recognize an arrival of the control lever to the proximity of the
control range.

8. A construction machine, comprising: a control-mode switching device of
a construction machine, the control-mode switching device including:a
plurality of actuators that conduct different movement;driving means that
respectively drive the plurality of actuators;a plurality of control
levers that command the movement of the driving means;a plurality of
detecting means that respectively detect arrival of the control levers to
the proximity of end of the control range of the control levers;a mode
judging means that judges whether a priority operation mode in which
output of selected one or more of the driving means becomes larger than
that in a normal mode or power ratio of the selected one or more of the
driving means as compared to the other driving means becomes larger is
taken or not based on a combination of detected conditions of the
detecting means; anda drive controlling means that, when it is judged by
the mode judging means that the priority operation mode is taken,
controls the driving means so that the output of the selected one or more
of the driving means becomes larger than that in the normal mode or the
power ratio of the selected one or more of the driving means as compared
to the other driving means becomes larger.

Description:

TECHNICAL FIELD

[0001]The present invention relates to a control-mode switching device of
a construction machine and a construction machine. More specifically, it
relates to a control-mode switching device and a construction machine
that are capable of easily switching the operation modes of a
construction machine such as an excavator.

BACKGROUND ART

[0002]A hydraulic excavator as shown in FIGS. 13A and 13B is known as a
construction machine for excavating and loading earth and sand, which
includes: a traveling hydraulic motor 1 for traveling a lower traveling
body a; a swing hydraulic motor 2 for swinging an upper swing body b;
work equipments c (a boom 3, an arm 4 and a bucket 5) mounted on the
front side of the upper swing body b; and a boom cylinder 6, arm cylinder
7 and bucket cylinder 8 for driving the work equipments c.

[0003]The hydraulic excavator performs a sequence of operations during an
excavating process such as excavation, lift-up swing, earth removal and
lift-down swing. Especially during the lift-up swing, while the boom is
lifted up and the arm is dumped (as shown in FIG. 13A), swing operation
is conducted toward a loading platform of a dumper truck d that is
stopped around forty-five, ninety or one-hundred-eighty degrees from the
excavated point (as shown in FIG. 13B).

[0004]When the swing and boom movements or the swing and arm movements are
concurrently conducted, pressure in swing circuit is influenced by boom
circuit or arm circuit, where, if the boom circuit or the arm circuit is
in low pressure, the swing circuit is also in low pressure, so that
smooth swing movement may not be conducted. Further, since the swing
angle differs according to the stop position of the dumper truck d, an
operator controls spool-opening degree of flow control valve of hydraulic
actuators for each operation to control supply flow rate toward
respective circuits to match both of the movements. For instance, the
supply flow rate to the respective circuits is controlled so that: when
the dumper truck d is stopped at forty-five degrees position from the
excavated point, the boom-lift movement is accelerated and swing speed is
decelerated; and, when the dumper truck d is stopped at one-hundred
eighty degrees position from the excavated point, the swing speed is
accelerated and boom-lift speed is decelerated, thereby matching both of
the movements. However, such operation is very difficult and exhausting.

[0005]Accordingly, the Applicant of the present application has proposed a
hydraulic control circuit of a hydraulic excavator for resolving the
above problems (Patent Document 1).

[0006]Specifically, the hydraulic control circuit of a hydraulic excavator
includes: hydraulic actuators respectively for boom-lifting, arm-lifting
and swinging movement; boom control lever; arm control lever; swing
control lever; hydraulic circuit for driving the hydraulic actuators
based on the operation on the control levers; and an operation-mode
selecting switch. When one of boom-priority mode, swing-priority mode and
standard mode is selected by the operation mode selecting switch,
pressure oil is preferentially flowed to the hydraulic circuit
corresponding to the selected mode.

[0007][Patent Document] Japanese Patent Publication No. 2583148

DISCLOSURE OF THE INVENTION

Problem to be Solved by the Invention

[0008]However, in the hydraulic control circuit of hydraulic excavator as
described in the above patent document 1, when the boom-priority mode or
the swing-priority mode is to be selected while operating the boom
control lever, arm control lever and swing control lever, one hand has to
be released from the control lever in order to switch the operation mode
selecting switch, resulting in troublesome switching operation.

[0009]An object of the present invention is to provide a control-mode
switching device and a construction machine capable of easily switching
operation modes.

Means for Solving the Problems

[0010]A control-mode switching device of a construction machine according
to an aspect of the present invention includes: a plurality of actuators
that conduct different movement; a driving means that respectively drives
the plurality of actuators; a plurality of control levers that command
movements of the driving means; a plurality of detecting means that
respectively detect arrival of the control levers to the proximity of
ends of the control ranges of the control levers; a mode judging means
that judges whether a priority operation mode in which output of selected
one or more of the driving means becomes larger than that in a normal
mode or power ratio of the selected one or more of the driving means as
compared to other driving means becomes larger is taken or not based on a
combination of detected conditions of the detecting means; and a drive
controlling means that, when it is judged by the mode judging means that
the priority operation mode is taken, controls the driving means so that
the output of the selected one or more of the driving means becomes
larger than that in the normal mode or the power ratio of the selected
one or more of the driving means as compared to other driving means
becomes larger.

[0011]The output of the driving means is speed, power and the like.
Further, that "output of selected one or more of the driving means
becomes larger than that in a normal mode" means that the output during
the priority operation mode becomes larger than the output during the
standard operation mode. That "the power ratio of the selected one or
more of the driving means as compared to the other driving means becomes
larger" means all of the situations where the power ratio is relatively
increased in relation to the output of the other driving means as in a
case where the output of the other driving means is lowered without
changing the output of the selected one or more of the driving means.

[0012]According to the above arrangement, when the control lever is
manipulated, the actuator is driven via the driving means. Accordingly,
desired operation can be executed by manipulating a plurality of control
levers to simultaneously or sequentially drive the plurality of
actuators.

[0013]During the operation, when it is desired to, for instance,
accelerate a certain actuator, the control lever for driving the actuator
is manipulated to the proximity of the end of the control range of the
lever. Then, the arrival of the control lever to the proximity of the
control range is detected by the detecting means. Subsequently, in
accordance with the combination of detected conditions of the detecting
means, whether the priority operation mode is taken or not is judged.
When it is judged that the priority operation mode is taken, the driving
means is controlled so that the output of the selected one or more
driving means corresponding to the priority operation mode becomes larger
than that in the normal mode or the power ratio as compared to the other
driving means becomes larger. Accordingly, the movement of the selected
actuator(s) can be, for instance, accelerated.

[0014]Accordingly, since the operation mode can be switched to the
priority operation mode only by manipulating the control lever to the
proximity of the end of the control range while manipulating the control
lever without releasing the control lever, the switching operation to the
priority operation mode can be facilitated.

[0015]In the above control-mode switching device of a construction
machine, the mode judging means preferably includes: a storing means that
stores a plurality of priority operation modes corresponding to the
combination of the detected conditions of the detecting means; and a
selecting means that selects the priority operation mode corresponding to
the combination of the detected conditions of the detecting means from
the storing means.

[0016]According to the above arrangement, since the plurality of priority
modes are stored in the storing means corresponding to the combination of
the detected conditions of the detecting means, the priority operation
mode set in accordance with the combination of the detected conditions of
the detecting means can be easily changed.

[0017]In the above control-mode switching device, the actuator is
preferably a hydraulic actuator, the driving means preferably includes a
hydraulic circuit and a flow-rate controlling means that controls a flow
rate of the hydraulic circuit, and, when it is judged by the mode judging
means that the priority operation mode is taken, the drive controlling
means preferably controls the flow-rate controlling means preferably so
that pressure oil supply that is supplied to selected one or more of the
hydraulic circuits becomes larger than pressure oil supply that is
supplied to the other hydraulic circuit.

[0018]According to the above arrangement, since the actuator includes a
hydraulic actuator and the respective driving means includes hydraulic
circuit, great force can be exerted when applied on a machine that
requires considerable power (e.g. excavator) and satisfactory excavating
operation can be achieved. Further, since the drive controlling means is
configured to control the flow-controlling means so that the pressure oil
supply supplied to the hydraulic circuit becomes larger than the pressure
oil supply supplied to the other hydraulic circuit, the drive controlling
means can be achieved with a relatively simple arrangement.

[0019]In the control-mode switching means of construction machine of the
present invention, an engine for driving the plurality of driving means
is preferably provided and the drive controlling means preferably
increases and decreases the power of the engine.

[0020]Alternatively, in the control-mode switching device of construction
machine of the present invention, a battery for driving the plurality of
driving means is preferably provided and the drive controlling means
preferably increases and decreases the power of the battery.

[0021]According to the above arrangement, since the priority operation
mode is conducted by increasing and decreasing the power of the engine
for executing the priority operation mode, the entire power can be
augmented.

[0022]In the above control-mode switching device, the actuator preferably
includes a hydraulic actuator, the driving means preferably include a
hydraulic circuit and a variable pressure-control valve that controls the
pressure in the hydraulic circuit, and, when it is judged by the mode
judging means that the priority operation mode is taken, the variable
pressure-control valve preferably is controlled so that pressure in the
selected one or more of the hydraulic circuits becomes larger.

[0023]According to the above arrangement, since the actuator is provided
by the hydraulic actuator and the respective driving means is provided by
the hydraulic circuit, where the priority operation mode is executed by
controlling the variable pressure-control valve provided in the hydraulic
circuit, simple arrangement can be achieved.

[0024]In the control-mode switching device of a construction machine of
the present invention, a notifying means that allows an operator to
recognize an arrival of the control lever to the proximity of the control
range is preferably provided.

[0025]According to the above arrangement, since the notifying means that
allows an operator to recognize the arrival of the control lever to the
proximity of the control range is provided, an operator can recognize the
arrival of the control lever to the proximity of the end of the control
range.

[0026]A construction machine according to another aspect of the invention
includes the above-described control-mode switching device of the present
invention.

[0027]According to the above arrangement, a construction machine having
the function of the above-described control-mode switching device can be
provided.

BRIEF DESCRIPTION OF DRAWINGS

[0028]FIG. 1 is a schematic illustration of a control lever according to a
first embodiment of the invention;

[0029]FIG. 2 is an illustration showing a relationship between control
force of a control lever and PPC pressure according to the first
embodiment;

[0030]FIG. 3 is a diagram showing a hydraulic control circuit according to
the first embodiment;

[0031]FIG. 4 is a diagram showing an internal arrangement of a controller
according to the first embodiment;

[0032]FIG. 5 is an illustration showing details of priority operation
modes according to the first embodiment;

[0033]FIG. 6 is an illustration showing details of priority operation
modes according to a modification of the first embodiment;

[0034]FIG. 7 is a flowchart of the above modification;

[0035]FIG. 8 is a diagram showing a hydraulic control circuit according to
a second embodiment of the invention;

[0036]FIG. 9 is a schematic illustration of a control lever according to
the second embodiment;

[0037]FIG. 10 is an illustration showing a relationship between control
force of a control lever and an output signal according to the second
embodiment;

[0038]FIG. 11 is a diagram showing a control system circuit according to a
third embodiment of the invention;

[0039]FIG. 12 is an illustration showing a modification of a control lever
of the invention;

[0040]FIG. 13A is an illustration for showing swing movement of an
excavator; and

[0041]FIG. 13B is another illustration for showing the swing movement of
the excavator.

[0043]An embodiment of the invention will be described below with
reference to attached drawings.

First Embodiment

[0044]FIG. 1 is a schematic illustration of a control lever used in the
present embodiment. FIG. 2 is an illustration showing output
characteristics of control force of the control lever and PPC (Pilot
Pressure Control) pressure.

[0045]A control lever 22 opens valves V1 and V2 in accordance with
operating direction and angle, so that pressure oil from a pilot pump P
is fed into pilot lines PT1 and PT2 through the valves V1 and V2.

[0046]When the stroke range of a normal control lever is 100%, the control
lever 22 can be operated to around 110%. When the operation stroke of the
control lever 22 exceeds 100%, an operation feeling is given where the
lever does not move without applying further greater control force. For
instance, when the operation stroke of the control lever 22 exceeds 100%,
movable part of the control lever 22 touches a biasing unit such as a
spring, so that a control force greater than the previous control force
is required for moving the lever on account of the reaction force of the
biasing unit.

[0047]A range in which the operation stroke of the control lever 22
exceeds 100% to be around 110% is called as a kickdown range (KDE). When
the control lever 22 reaches to the kickdown range, i.e. when the control
lever 22 reaches to the proximity of the end of manipulable range, limit
switches (detecting means) LS1 and LS2 are turned on, thereby detecting
that the control lever 22 has reached to the kickdown range. The PPC
pressure output within the kickdown range stays the same.

[0048]Among the hydraulic control circuits, a hydraulic control circuit of
three hydraulic actuators, i.e. boom-driving hydraulic cylinder (referred
to as a boom cylinder hereinafter) 6, arm-driving hydraulic cylinder
(referred to as an arm cylinder hereinafter) 7 and swing hydraulic motor
2 according to the present invention, are shown in FIG. 3.

[0049]The hydraulic control circuit is a two-pump type including two
variable displacement hydraulic pumps 10 and 13. The boom cylinder 6 is
connected to a delivery line 11 of the variable displacement hydraulic
pump 10 via a pressure compensated flow-control valve 12 for controlling
the flow rate and flow direction. A delivery line 14 of the variable
displacement hydraulic pump 13 includes two branch lines 14a and 14b. The
swing hydraulic motor 2 is connected to the branch line 14a via a
pressure compensated flow-control valve 15. The arm cylinder 7 is
connected to the branch line 14b via a pressure compensated flow-control
valve 16.

[0050]Incidentally, the variable displacement hydraulic pumps 10 and 13
are driven by an engine 91 (in FIG. 3, though it is illustrated that the
engine 91 is connected respectively to the pumps 10 and 13, the pumps 10
and 13 are actually driven by the single engine 91), where the maximum
engine speed and maximum power of the engine 91 is controlled by a
command signal of a controller 23 through a governor (not shown).

[0051]The boom cylinder 6, the arm cylinder 7 and the swing hydraulic
motor 2 are connected to the two variable displacement hydraulic pump 10
and 13 in parallel, and are also connected to a reservoir 18 through a
return circuit 17.

[0052]The pressure compensated flow-control valves 12, 15 and 16 are
pilot-operated type. A main line 20 of a pilot pump 19 are connected to
both ends of the respective pressure compensated flow-control valves 12,
15 and 16 via pilot lines 73a to 73f of the respective control levers
22a, 22b and 22c.

[0053]A limit switch 72a for detecting that the control lever 22c reaches
to the kickdown range when the control lever 22c is operated in
boom-lift-up direction is provided on the boom control lever 22c: a limit
switch 72b for detecting that the control lever 22b reaches to the
kickdown range when the control lever 22b is operated in both right and
left rotary directions is provided on the swing control lever 22b: and
limit switches 72c and 72d for detecting that the control lever 22a
reaches to the kickdown range when the control lever 22a is operated in
arm excavating direction are provided on the arm control lever 22a.

[0055]Variable displacement pressure-control valves 67 and 66 are
connected to the delivery lines 11 and 14 of the variable displacement
hydraulic pumps 10 and 13. When the pilot valves 61 and 63 are switched
by a command signal output from the controller 23 through the signal
circuits 60 and 62, pilot pressure from the pilot pump 19 is applied to
an operating section of the variable pressure-control valves 67 and 66
through pilot lines 64 and 65. Accordingly, maximum pressure (relief
pressure) of the delivery lines 11 and 14 of the variable displacement
hydraulic pumps 10 and 13 are controlled. Incidentally, 26 denotes a
return line of the pilot hydraulic pressure.

[0056]The pressure compensated flow-control valves 12, 15 and 16 are
provided with a mechanism for restricting a spool stroke within the
control valves to control maximum flow rate. When the pilot valves 75b,
75c and 75d are switched by a command signal output from the controller
23 through the signal circuits 74b, 74c and 74d, the pilot pressure from
the pilot pump 19 is applied to the operating section of the respective
pressure compensated flow-control valves 12 and 15 to restrict the flow
rate of the pressure compensated flow-control valves 12 and 15.

[0058]Pressure compensating valves 27a, 27b and 27c for detecting and
compensating discharge pressure of the hydraulic pumps 10 and 13 relative
to the required flow rate of the respective actuators (the boom cylinder
6, the arm cylinder 7 and the swing hydraulic motor 2) are provided on
the pressure compensated flow-control valves 12, 15 and 16. The pressure
compensating valves 27a, 27b and 27c are connected to load sensing
regulators 28a and 28b of the hydraulic pumps 10 and 13 through pilot
lines 29a and 29b.

[0059]The load sensing circuit is configured as follows. The pressure on
the maximum load pressure side of a pilot line 33 for detecting the
maximum load pressure of the swing hydraulic motor 2 from an outlet port
32 of the pressure compensated flow-control valve 15 and a pilot line 31
for detecting the maximum load pressure of the arm cylinder 7 from an
output port 30 of the pressure compensated flow-control valve 16 is
detected by a shuttle valve 34. The pressure on the maximum load pressure
side of a pilot line 35 connected to the shuttle valve 34 and a pilot
line 37 for detecting the maximum load pressure of the boom cylinder 6
from the outlet port 36 of the pressure compensated flow-control valve 12
is detected by a shuttle valve 38, which on one hand is input to the load
sensing regulator 28a of the hydraulic pump 10 through the pilot line 29a
and on the other hand is input to the load sensing regulator 28b of the
other hydraulic pump 13 through the pilot line 29b.

[0060]A swing load sensing switching valve 40 is provided on the load
sensing circuit. The switching valve 40 is controllably switched by an
electromagnetic pilot valve 52 controlled by a signal circuit 51 of the
controller 23 through a pilot line 41.

[0061]The load sensing regulators 28a and 28b respectively include
pilot-operated load sensing valves 44a and 44b provided between the
delivery lines 11 and 14 and servo pistons 42a and 42b for controlling
swash-plate inclination of the hydraulic pumps 10 and 13. Pilot lines 29a
and 43a are connected to both ends of one of the load sensing valves 44a,
and pilot lines 29b and 43b are connected to both ends of the other load
sensing valve 44b.

[0062]When the sum of the maximum load pressure introduced by the pilot
lines 29a and 29b and spring force of springs 45a and 45b becomes greater
than the discharge pressure of the hydraulic pumps 10 and 13 introduced
by the pilot lines 43a and 43b, the load sensing valves 44a and 44b
switches from (A) position to (B) position to return the pressure oil of
the servo pistons 42a and 42b to the reservoir 18 to increase swash-plate
angle of the hydraulic pumps 10 and 13 to augment the discharge flow
rate. On the contrary, when the sum of the maximum load pressure and the
spring force becomes smaller than the discharge pressure of the hydraulic
pumps 10 and 13, the load sensing valves 44a and 44b switches from the
(B) position to the (A) position, so that the pressure oil from the pilot
lines 43a and 43b enters into the servo pistons 42a and 42b to decrease
the swash-plate angle of the hydraulic pumps 10 and 13 to reduce the
discharge flow rate.

[0063]In other words, the discharge pressure P1 of the hydraulic pump 10
is applied from the line 43a to one of the operating sections of the load
sensing valve 44a, and the load pressure LP1 introduced by the pilot line
29a and the spring force are applied on the other operating section of
the load sensing valve 44a. Accordingly, when P1>LP1, the swash-plate
angle of the hydraulic pump 10 is controlled to be decreased, and, when
P1<LP1, the swash-plate angle of the hydraulic pump 10 is controlled
to be increased.

[0064]Further, the discharge pressure P2 of the hydraulic pump 13 is
applied from the line 43a to one of the operating sections of the load
sensing valve 44b, and the load pressure LP2 introduced by the pilot line
29b and the spring force are applied on the other operating section of
the load sensing valve 44b. Accordingly, when P2>LP2, the swash-plate
angle of the hydraulic pump 13 is controlled to be decreased, and, when
P2<LP2, the swash-plate angle of the hydraulic pump 13 is controlled
to be increased.

[0065]With the use of the above load sensing system and the pressure
compensated flow-control valves 12, 15 and 16, while restraining the
discharged pressure oil of the hydraulic pumps 10 and 13 to a required
flow rate to serve for energy saving, the respective pressure
compensating valves 27a, 27b and 27c are controlled by the maximum load
pressure of the respective hydraulic actuators (the boom cylinder 6, the
arm cylinder 7 and the swing hydraulic motor 2).

[0066]The delivery lines 11 and 14 of the two variable displacement
hydraulic pumps 10 and 13 are interconnected by a communication line 46.
The communication line 46 is provided with a merge/branch switching valve
47 of the discharged pressure oil of both of the hydraulic pumps 10 and
13. The switching valve 47 is controllably switched by pilot pressure of
a pilot line 48 in accordance with actuation of an electromagnetic pilot
valve 50 commanded by the controller 23 via a signal circuit 49.

[0068]The hydraulic control circuit having thus arranged load-sensing
system is operated under various priority modes set in advance in the
controller 23 so that operation matching can be changed by flow-rate
distribution for simultaneous operation of the swing mechanism and the
boom or arm while excavating earth and sand with lift-up swing and
loading into a dumper truck, and instantaneous operation under a
predetermined rated power of an engine can be conducted when hard soil is
to be excavated.

[0069]Specifically, as shown in FIG. 4, the controller 23 includes: a mode
judging unit 23A that judges whether a priority operation mode in which
an output of selected one or more of the driving means can be set higher
than a normal mode or output ratio can be set higher as compared to the
other driving means is taken or not in accordance with the signals from
the limit switches 72a, 72c, 72d and 72e provided on the respective
control levers 22a, 22b and 22c; and a drive controlling means 23B that
controls the driving means so that, when the mode judging unit 23A judges
that the priority operation mode is taken, an output of selected one or
more of the driving means corresponding to the priority operation mode is
set higher than that in the normal mode or the output ratio is set higher
as compared to the other driving means.

[0070]The mode judging unit 23A includes a storing means 23A1 that stores
a plurality of priority operation modes in accordance with the
combination of on/off conditions of the limit switches 72a, 72c, 72d and
72e, and a selecting means 23A2 that selects a priority operation mode
corresponding to the combination of on/off conditions of the limit
switches 72a, 72c, 72d and 72e from the storing means 23A1.

[0071]The drive controlling means 23B transmit a command signal to the
pilot valve 50, the pilot valves 75b to 75d, the pilot valve 52 and the
pilot valves 61 and 63 in accordance with the priority operation mode
selected by the mode judging unit 23A to perform the priority operation
mode.

[0073]Incidentally, 55 denotes a monitor, on which respective operation
modes are displayed.

(1) Standard Mode

[0074]When (1) ninety-degree swing operation and boom-lift-up operation
are simultaneously conducted and (2) approximately the same flow rate is
desired without giving priority to one of the swinging movement and the
boom movement and instantaneous increase in excavating force and engine
power is not necessary, the respective control levers 22a, 22b and 22c
are operated within a normal stroke range. In other words, the control
levers are used without reaching to the kickdown range.

[0075]Under the above condition, the command signal from the controller 23
is not transmitted to the pilot valve 50. Accordingly, since the pilot
valve 50 is located at the position shown in FIG. 3, the pilot pressure
applied on the operating section of the merge/branch switching valve 47
is drained from the pilot line 48 to the reservoir 18 and the
merge/branch switching valve 47 is off-driven to be positioned at a merge
position shown in FIG. 3. In other words, the pressure oil from the
hydraulic pump 10 and the pressure oil from the hydraulic pump 13 are
merged through the merge/branch switching valve 47.

[0076]When the boom control lever 22c is operated under this condition,
the pressure oil from the pilot pump 19 is applied to the operating
section of the pressure compensated flow-control valve 12 through the
pilot lines 73a and 73b to advance and retract the boom cylinder 6. In
other words, the boom is lifted up and down.

[0077]When the swing lever 22b is operated, the pressure oil from the
pilot pump 19 is applied to the operating section of the pressure
compensated flow-control valve 15 through the pilot lines 73c and 73d.
Consequently, the swing hydraulic motor 2 is turned clockwise and
counterclockwise. In other words, swinging movement is conducted.

[0078]When the arm control lever 22a is operated, the pressure oil from
the pilot pump 19 is applied to the operating section of the pressure
compensated flow-control valve 16 through the pilot lines 73e and 73f to
advance and retract the arm cylinder 7.

[0079]On the other hand, the command signal from the controller 23 is
transmitted to the pilot valve 52 in the standard mode. Then, since the
pilot valve 52 is switched, the pilot pressure from the pilot pump 19 is
applied to the operating section of the swing load sensing switching
valve 40 from the pilot line 41 through the pilot valve 52, so that the
swing load sensing switching valve 40 is on-driven to be at "cutoff"
position.

[0080]Accordingly, the load pressure for driving the swing hydraulic motor
2 is blocked by the swing load sensing switching valve 40, the load
pressure of the boom cylinder 6 is detected by the shuttle valve 38. The
load pressure is applied to the load sensing valve 44a through the pilot
line 29a and is also applied to the operating section of the load sensing
valve 44b through the pilot line 29b.

[0081]Accordingly, the discharge pressure P1 of the hydraulic pump 10 is
applied from the line 43a to one of the operating sections of the load
sensing valve 44a, and the load pressure LP1 introduced by the pilot line
29a and the spring force are applied on the other operating section of
the load sensing valve 44a. As a result, when P1>LP1, the swash-plate
angle of the hydraulic pump 10 is controlled to be decreased, and, when
P1<LP1, the swash-plate angle of the hydraulic pump 10 is controlled
to be increased.

[0082]Further, the discharge pressure P2 of the hydraulic pump 13 is
applied from the line 43a to one of the operating sections of the load
sensing valve 44b, and the load pressure LP2 of the boom cylinder 6
introduced by the pilot line 29b and the spring force are applied on the
other operating section of the load sensing valve 44b. As a result, when
P2>LP2, the swash-plate angle of the hydraulic pump 13 is controlled
to be decreased, and, when P2<LP2, the swash-plate angle of the
hydraulic pump 13 is controlled to be increased.

[0083]In other words, when the boom and swing mechanism are simultaneously
operated in the standard mode, the swash-plate angle of the hydraulic
pumps 10 and 13 are controlled to correspond to the load pressure of the
boom actuator (the boom cylinder 6) to supply required flow to the
respective actuators of the boom and the swing mechanisms (the boom
cylinder 6 and the swing hydraulic motor 2).

(II) Excavating Power-Up Mode (Single Operation)

[0084]For instance, when the arm is solely operated for excavation, the
arm control lever 22a is operated to the kickdown range beyond the normal
range.

[0085]Accordingly, a command signal from the controller 23 is transmitted
to the pilot valve 61. Then, the pilot valve 61 is switched and the pilot
pressure from the pilot pump 19 is applied to the operating section of
the variable pressure-control valve 66 from the pilot line 64 through the
pilot valve 61. As a result, the variable pressure-control valve 66 is
on-driven to be located at boost position. In other words, the drive
hydraulic circuit of the arm cylinder 7 is boosted (110% boosted relative
to rated pressure), so that excavating force can be temporarily increased
during the operation.

[0086]Similarly, when the swing mechanism is solely operated, the swing
control lever 22b is manipulated to the kickdown range beyond the normal
range for temporarily increasing the swing power during the operation.

[0087]Further, when the boom is solely lifted up, the boom control lever
22c is manipulated to the kickdown range beyond the normal range.

[0088]Accordingly, a command signal from the controller 23 is transmitted
to the pilot valve 63. Then, the pilot valve 63 is switched and the pilot
pressure from the pilot pump 19 is applied to the operating section of
the variable pressure-control valve 67 from the pilot line 65 through the
pilot valve 63. As a result, the variable pressure-control valve 67 is
on-driven to be located at boost position. In other words, the drive
hydraulic circuit of the boom cylinder 6 is boosted (110% boosted
relative to rated pressure), so that boom-lifting force can be
temporarily increased during the operation.

(III) Swing Priority Mode (Swinging Force and Speed Up)

[0089]For instance, when (1) one-hundred-eighty degree swing and boom
lift-up are simultaneously conducted and (2) load pressure on the swing
hydraulic motor 2 is great and large amount of flow is necessary or
temporary increase in swinging force is required for operation, only the
swing control lever 22b is solely manipulated to the kickdown range
beyond the normal range.

[0090]Accordingly, a command signal from the controller 23 is transmitted
to the pilot valve 50. Then, the pilot valve 50 is switched and the pilot
pressure from the pilot pump 19 is applied to the operating section of
the merge/branch switching valve 47 from the pilot line 48 through the
pilot valve 50. As a result, the merge/branch switching valve 47 is
on-driven to be located at branch position.

[0091]At this time, the pilot pressure from the pilot pump 19 is applied
to the operating section of the load sensing pressure on/off switching
valve 53 to switch the load sensing pressure on/off switching valve 53 to
"a" position.

[0092]Simultaneously, a command signal from the controller 23 is
transmitted to the pilot valve 75b. Then, the pilot valve 75b is switched
and the pilot pressure from the pilot pump 19 is applied to lowering side
operating section of the pressure compensated flow-control valve 12 from
the pilot valve 75b. As a result, raising-side spool stroke in the
pressure compensated flow-control valve 12 is restricted, thereby
regulating boom-raising side flow rate.

[0093]Further, a command signal from the controller 23 is transmitted to
the pilot valve 61. Then, the pilot valve 61 is switched and the pilot
pressure from the pilot pump 19 is applied to the operating section of
the variable pressure-control valve 66 from the pilot line 64 through the
pilot valve 61. As a result, the variable pressure-control valve 66 is
on-driven to be located at boost position. In other words, the drive
hydraulic circuit of the swing hydraulic motor 2 is boosted (110% boost
relative to rated pressure), so that only the swing force can be
temporarily increased for simultaneously conducting the swing operation
and boom-lift-up operation.

[0094]On the other hand, the command signal from the controller 23 is not
transmitted to the pilot valve 52. Accordingly, the pilot pressure
applied to the pilot valve 52 is drained from the line 41 to the
reservoir 18, so that the pilot valve 52 is off-driven to be switched to
"link" position shown in FIG. 3.

[0095]Accordingly, the load pressure for driving the swing hydraulic motor
2 is applied to the operating section of the load sensing valve 44b
through the swing load sensing switching valve 40, the shuttle valve 34,
the pilot line 35, "a" position of the load sensing pressure on/off
switching valve 53 and the pilot line 29b.

[0096]Accordingly, the discharge pressure P2 of the hydraulic pump 13 is
applied from the line 43a to one of the operating sections of the load
sensing valve 44b, and the load pressure LP2 of the swing hydraulic motor
2 introduced by the pilot line 29b and the spring force are applied on
the other operating section of the load sensing valve 44b. As a result,
when P2>LP2, the swash-plate angle of the hydraulic pump 13 is
controlled to be decreased, and, when P2<LP2, the swash-plate angle of
the hydraulic pump 13 is controlled to be increased.

[0097]Accordingly, when the swing priority mode is selected, the hydraulic
pump 13 independently supplies required flow rate to the swing hydraulic
motor 2 and the drive circuit pressure can be boosted. In this case, the
boom cylinder 6 is controlled based on differential pressure between the
discharge pressure P1 and the load pressure LP1 as in the above standard
mode. However, since the spool stroke of the pressure compensated
flow-control valve 12 is restricted, the flow rate from the hydraulic
pump 10 is also restricted.

[0098]In other words, when the boom movement and swing movement are
simultaneously conducted in the swing priority mode, the flow rate from
the hydraulic pump 10 to the boom actuator (boom cylinder 6) is
regulated, and since the swash-plate angle of the hydraulic pump 13 is
regulated corresponding to the load pressure simultaneously with the
boosting of the drive hydraulic circuit of the swing actuator (swing
hydraulic motor 2), the drive force and required flow rate of the swing
hydraulic motor 2 are augmented.

(IV) Boom-Up Priority Mode (Boom-Up Excavating Force and Speed Up)

[0099]For instance, when the swing operation and the boom-up operation are
simultaneously conducted and (1) swing angle is relatively small
(forty-five degrees for instance) and (2) large amount of flow rate is
required for boom-up operation or temporary increase in boom-up force is
required for operation, only the boom control lever 22c is manipulated to
the kickdown range beyond the normal range.

[0100]Accordingly, a command signal from the controller 23 is transmitted
to the pilot valve 50. Then, the pilot valve 50 is switched and the pilot
pressure from the pilot pump 19 is applied to the operating section of
the merge/branch switching valve 47 from the pilot line 48 through the
pilot valve 50. As a result, the branch switching valve 47 is on-driven
to be located at branch position.

[0101]At this time, the pilot pressure from the pilot pump 19 is applied
to the operating section of the load sensing pressure on/off switching
valve 53 to switch the load sensing pressure on/off switching valve 53 to
"a" position.

[0102]Simultaneously, a command signal from the controller 23 is
transmitted to the pilot valve 52. Then, the pilot valve 52 is switched
and the pilot pressure from the pilot pump 19 is applied to the operating
section of the swing load sensing switching valve 40 from the pilot line
41 through the pilot valve 52. As a result, the load pressure for driving
the swing hydraulic motor 2 is blocked by the swing load sensing
switching valve 40.

[0103]Further, the command signal from the controller 23 is transmitted to
the pilot valve 75c or the pilot valve 75d. Then, the pilot valve 75c or
the pilot valve 75d is switched, so that the pilot pressure from the
pilot pump 19 is applied from the pilot valve 75c or the pilot valve 75d
to the side opposite to the driving side operating section of the
pressure compensated flow-control valve 15. As a result, driving-side
spool stroke inside the pressure compensated flow-control valve 15 is
restricted to regulate the swing flow rate.

[0104]Further, a command signal from the controller 23 is transmitted to
the pilot valve 63. Then, the pilot valve 63 is switched and the pilot
pressure from the pilot pump 19 is applied to the operating section of
the variable pressure-control valve 67 from the pilot line 65 through the
pilot valve 63. As a result, the variable pressure-control valve 67 is
on-driven to be located at boost position.

[0105]In other words, the drive hydraulic circuit of the boom cylinder 6
is boosted (110% boost relative to rated pressure), so that only the
boom-up force can be temporarily increased for simultaneously conducting
the swing operation and boom-lift-up operation.

[0106]On the other hand, the load pressure of the boom cylinder 6 is
applied to the operating section of the load sensing valve 44a through
the pilot line 29a, and the load pressure of the swing hydraulic motor 2
is not applied to the operating section of the load sensing valve 44b.

[0107]Accordingly, the discharge pressure P1 of the hydraulic pump 10 is
applied from the line 43a to one of the operating sections of the load
sensing valve 44a, and the load pressure P1 introduced by the pilot line
29a and the spring force are applied on the other operating section of
the load sensing valve 44a. As a result, when P1 (discharge pressure of
hydraulic pump 10)>LP1 (load pressure of the boom cylinder), the
swash-plate angle of the hydraulic pump 10 is controlled to be decreased,
and, when P1<LP1, the swash-plate angle of the hydraulic pump 10 is
controlled to be increased.

[0108]Further, when the load pressure from the swing hydraulic motor 2 is
not applied to the load sensing valve 44b, the load sensing valve 44b is
controlled by the discharge pressure P2 of the hydraulic pump 13. When
the discharge pressure P2 becomes greater than the spring force, the
swash-angle plate is controlled to be decreased.

[0109]Accordingly, when the boom-up operation and the swing operation are
simultaneously conducted in the boom-up priority mode, the flow rate from
the hydraulic pump 13 to the swing actuator (swing hydraulic motor 2) is
regulated, and, simultaneously with the boosting of the drive hydraulic
circuit of the boom actuator (boom cylinder 6), the swash-plate angle of
the hydraulic pump 10 is controlled corresponding to the load pressure,
so that drive force and required flow rate of the boom cylinder 6 are
augmented.

[0110]Incidentally, when the arm cylinder 7 is driven, the load pressure
of the arm is applied to the operating section of the load sensing valve
44b through the shuttle valve 34, the pilot line 35, the "a" position of
the switching valve 53 and the pilot line 29b. Accordingly, when
P2>LP2, the swash-plate angle of the hydraulic pump 13 is controlled
to be decreased, and, when P2<LP2, the swash-plate angle of the
hydraulic pump 13 is controlled to be increased, so that required flow
rate can be supplied to the arm cylinder 7.

(V) Arm Excavation Priority Mode (Arm Excavating Power and Speed Up)

[0111]For instance, when arm-excavation operation and boom-up operation
are simultaneously conducted for rough finish and (1) arm-excavation
speed has to be accelerated or (2) only arm excavating power is
temporarily increased, only the arm control lever 22a is manipulated to
the kickdown range beyond the normal range.

[0112]Accordingly, a command signal from the controller 23 is transmitted
to the pilot valve 50. Then, the pilot valve 50 is switched and the pilot
pressure from the pilot pump 19 is applied to the operating section of
the merge/branch switching valve 47 from the pilot line 48 through the
pilot valve 50. As a result, the branch switching valve 47 is on-driven
to be located at branch position.

[0113]At this time, the pilot pressure from the pilot pump 19 is applied
to the operating section of the load sensing pressure on/off switching
valve 53 to switch the load sensing pressure on/off switching valve 53 to
"a" position.

[0114]Simultaneously, a command signal from the controller 23 is
transmitted to the pilot valve 52. Then, the pilot valve 52 is switched
and the pilot pressure from the pilot pump 19 is applied to the operating
section of the swing load sensing switching valve 40 from the pilot line
41 through the pilot valve 52. As a result, the load pressure for driving
the swing hydraulic motor 2 is blocked by the swing load sensing
switching valve 40.

[0115]Further, a command signal from the controller 23 is transmitted to
the pilot valve 75. Then, the pilot valve 75b is switched and the pilot
pressure from the pilot pump 19 is applied to the lowering side operating
section of the pressure compensated flow-control valve 12 from the pilot
valve 75b. As a result, the raising-side spool stroke in the pressure
compensated flow-control valve 12 is restricted, thereby regulating the
boom-raising side flow rate.

[0116]Further, a command signal from the controller 23 is transmitted to
the pilot valve 61. Then, the pilot valve 61 is switched and the pilot
pressure from the pilot pump 19 is applied to the operating section of
the variable pressure-control valve 66 from the pilot line 64 through the
pilot valve 61. As a result, the variable pressure-control valve 66 is
on-driven to be located at boost position.

[0117]In other words, the drive hydraulic circuit of the arm cylinder 7 is
boosted (110% boost relative to rated pressure), so that only the
arm-excavating force can be temporarily increased for simultaneously
conducting the arm excavating operation and boom-lift-up operation.

[0118]On the other hand, the load pressure of the arm cylinder 7 is
applied to the operating section of the load sensing valve 44b through
the pilot line 29b, and the load pressure of the swing hydraulic motor 2
is not applied to the operating section of the load sensing valve 44b.

[0119]Accordingly, the discharge pressure P2 of the hydraulic pump 13 is
applied from the line 43a to one of the operating sections of the load
sensing valve 44b, and the load pressure LP2 of the arm cylinder 7
introduced by the pilot line 29b and the spring force are applied on the
other operating section of the load sensing valve 44b.

[0120]As a result, when P2 (discharge pressure of hydraulic pump
13)>LP2 (load pressure of the arm cylinder 7), the swash-plate angle
of the hydraulic pump 13 is controlled to be decreased, and, when
P2<LP2, the swash-plate angle of the hydraulic pump 13 is controlled
to be increased.

[0121]In other words, when the boom-up movement and arm-excavation are
simultaneously conducted in the arm-excavation priority mode, the flow
rate from the hydraulic pump 10 to the boom actuator (boom cylinder 6) is
regulated, and since the swash-plate angle of the hydraulic pump 13 is
regulated corresponding to the load pressure simultaneously with the
boosting of the drive hydraulic circuit of the arm actuator (arm cylinder
7), the drive force and required flow rate of the arm cylinder 7 are
augmented.

(VI) Power-Up Mode (Swing+Boom-Up)

[0122]In some cases, it is desirable to increase power for rapid loading
operation and the like. For instance, when large amount of flow is
required to both actuators in order to simultaneously accelerate the
boom-up speed and the swing speed, the swing control lever 22b and the
boom control lever 22c are manipulated to the kickdown range beyond the
normal range.

[0123]Under the above condition, the command signal from the controller 23
is not transmitted to the pilot valve 50. Accordingly, since the pilot
valve 50 is located at the position shown in FIG. 3, the pilot pressure
applied on the operating section of the merge/branch switching valve 47
is drained from the pilot line 48 to the reservoir 18 and the
merge/branch switching valve 47 is off-driven to be positioned at a merge
position shown in FIG. 3. In other words, the pressure oil from the
hydraulic pump 10 and the pressure oil from the hydraulic pump 13 are
merged through the merge/branch switching valve 47.

[0124]On the other hand, a command signal from the controller 23 is
transmitted to the pilot valve 52. Then, the pilot valve 52 is switched
and the pilot pressure from the pilot pump 19 is applied to the operating
section of the swing load sensing switching valve 40 from the pilot line
41 through the pilot valve 52. As a result, the load pressure for driving
the swing hydraulic motor 2 is blocked by the swing load sensing
switching valve 40.

[0125]Simultaneously, a command signal from the controller 23 is
transmitted to the pilot valves 61 and 63. Then, the pilot valves 61 and
63 are switched and the pilot pressure from the pilot pump 19 is applied
to the operating section of the variable pressure-control valves 66 and
67 from the pilot lines 64 and 65 through the pilot valves 61 and 63. As
a result, the variable pressure-control valves 66 and 67 are on-driven to
be located at boost position.

[0126]Further, the command signal from the controller 23 is transmitted to
a governor (not shown) for controlling the speed and power of the engine
for driving the hydraulic pumps 10 and 13. Then, the speed and power of
the engine is controlled to be raised (about 100% relative to rated speed
and power).

[0127]In other words, the speed and power of the engine for driving the
hydraulic pumps 10 and 13 are increased, the boom-up speed and swing
speed can be simultaneously raised in the loading operation and the like,
so that loading operation can be speedily conducted.

[0128]On the other hand, the load pressure of the arm cylinder 7 is
applied to the operating section of the load sensing valve 44b through
the pilot line 29b, and the load pressure of the swing hydraulic motor 2
is not applied to the operating section of the load sensing valve 44b.

[0129]Accordingly, the discharge pressure P2 of the hydraulic pump 13 is
applied from the line 43a to one of the operating sections of the load
sensing valve 44b, and the load pressure LP2 of the arm cylinder 7
introduced by the pilot line 29b and the spring force are applied on the
other operating section of the load sensing valve 44b. As a result, when
differential pressure of the discharge pressure P2 of hydraulic pump 13
and the load pressure LP2 of the arm cylinder 7 is P2>LP2, the
swash-plate angle of the hydraulic pump 13 is controlled to be decreased,
and, when P2<LP2, the swash-plate angle of the hydraulic pump 13 is
controlled to be increased.

(VII) Power-Up Mode (Boom-Up+Arm-Excavation)

[0130]Similarly, large amount of flow is required to both actuators in
order to simultaneously accelerate the boom-up speed and the
arm-excavation speed, the boom control lever 22c and the arm control
lever 22a are manipulated to the kickdown range beyond the normal range.

[0131]Under the above condition, the command signal from the controller 23
is not transmitted to the pilot valve 50. Accordingly, since the pilot
valve 50 is located at the position shown in FIG. 3, the pilot pressure
applied on the operating section of the merge/branch switching valve 47
is drained from the pilot line 48 to the reservoir 18 and the
merge/branch switching valve 47 is off-driven to be positioned at a merge
position shown in FIG. 3. In other words, the pressure oil from the
hydraulic pump 10 and the pressure oil from the hydraulic pump 13 are
merged through the merge/branch switching valve 47.

[0132]On the other hand, a command signal from the controller 23 is
transmitted to the pilot valve 52. Then, the pilot valve 52 is switched
and the pilot pressure from the pilot pump 19 is applied to the operating
section of the swing load sensing switching valve 40 from the pilot line
41 through the pilot valve 52. As a result, the load pressure for driving
the swing hydraulic motor 2 is blocked by the swing load sensing
switching valve 40.

[0133]Simultaneously, a command signal from the controller 23 is
transmitted to the pilot valves 61 and 63. Then, the pilot valves 61 and
63 are switched and the pilot pressure from the pilot pump 19 is applied
to the operating section of the variable pressure-control valves 66 and
67 from the pilot lines 64 and 65 through the pilot valves 61 and 63. As
a result, the variable pressure-control valves 66 and 67 are on-driven to
be located at boost position.

[0134]Further, the command signal from the controller 23 is transmitted to
a governor (not shown) for controlling the speed and power of the engine
91 for driving the hydraulic pumps 10 and 13. Then, the speed and power
of the engine 91 is controlled to be raised (about 100% relative to rated
speed and power).

[0135]In other words, since the speed and power of the engine 91 for
driving the hydraulic pump 10 and 13 increase, the boom-up speed and the
arm-excavation speed can be simultaneously accelerated, so that
excavation operation and the like can be speedily conducted.

[0136]Incidentally, since the swash-plate angle control of the hydraulic
pumps 10 and 13 is the same as the effect of the above-described (VI),
explanation thereof is omitted.

(VIII) Power-Up Mode (Swing+Arm Excavation)

[0137]When large amount of flow is required on both of the actuators for
simultaneously increasing arm-excavation speed and swing speed in order
to temporarily increase the power for speedy swing ground-smoothing and
the like, the arm control lever 22a and the swing control lever 22b are
manipulated to the kickdown range beyond the normal range.

[0138]The effect of the above arrangement is the same as the effect of the
above-described (VI) and the explanation thereof is not described.

<Modification of First Embodiment>

[0139]Though one limit switch 72a is provided on the boom control lever
22c, two limit switches 72c and 72d are provided on the swing control
lever 22b and one limit switch 72e is provided on the arm control lever
22a, a bucket control lever may be provided in addition to the boom
control lever 22c, the swing control lever 22b and the arm control lever
22a and two limit switches for detecting the kickdown range may be
provided to the control levers to set the priority operation modes in
accordance with the combination of on/off conditions of the limit
switches.

[0140]For instance, as shown in FIG. 6, excavating power up mode, boom
priority mode, arm priority mode, bucket priority mode, swing priority
mode and power-up mode may be set in accordance with the combination of
on/off conditions of boom switch BSW1 (up, down), arm switch ASW
(excavation, dump), bucket switch BSW2 (excavation, dump) and swing
switch TSW (right, left), and corresponding mode may be selected and
executed based on the combination of on/off conditions of the switch.

[0141]During execution process, as shown in FIG. 7, after on/off
conditions of the switches are determined (ST1), the mode is judged based
on the combination of the on/off conditions of the switches (ST2).
Specifically, whether the combination of the on/off conditions of the
switches is included in the designated modes shown in FIG. 6 or not is
judged. When the combination is not included in the designated operation
modes, normal operation is conducted as the standard mode (normal mode)
(ST3).

[0143]Subsequently to the excavating power-up mode (ST4), the variable
pressure-control valve is boosted (ST10). Specifically, the variable
pressure-control valves 66 and 67 are switched to the boost position.

[0144]In the boom priority mode (ST5), after control flow rate other than
the boom is slightly reduced in the respective driving hydraulic
circuits, the process of ST10 is conducted. In the arm priority mode
(ST6), after control flow rate other than the arm is slightly reduced in
the respective driving hydraulic circuits, the process of ST10 is
conducted. In the bucket priority mode (ST7), after control flow rate
other than the bucket is slightly reduced in the respective driving
hydraulic circuits, the process of ST10 is conducted. In the swing
priority mode (ST8), after control flow rate other than the swing
mechanism is slightly reduced in the respective driving hydraulic
circuits, the process of ST10 is conducted. In the power-up mode (ST9),
after raising the power of the engine 91, the process of ST10 is
conducted.

[0145]In the above examples, since the control flow rate of the drive
hydraulic circuit other than the selected priority operation mode is
restrained to increase the control flow rate of the hydraulic circuit
corresponding to the selected priority operation mode relative to the
control flow rate of the other hydraulic circuits. Consequently, priority
is given to the hydraulic circuit corresponding to the selected priority
operation mode. In this arrangement, existing hydraulic circuit can be
used for implementing the present invention.

Second Embodiment

[0146]FIG. 8 shows a hydraulic control circuit of a hydraulic excavator
according to second embodiment of the invention. The hydraulic control
circuit of the present embodiment differs from the hydraulic control
circuit of the first embodiment in the following.

[0147]The PPC type control levers 22a, 22b and 22c, the limit switches
72a, 72c and 72d, the main line 20 and the pilot lines 73a, 73b, 73c,
73d, 73e and 73f are omitted from the first embodiment and electric
control levers 22d, 22e and 22f are provided in place thereof. In this
connection, pilot valves (electromagnetic proportional control valve)
25a, 25b, 25c, 25d, 25e and 25f are provided to the controller 23 via
signal circuits 24a, 24b, 24c, 24d, 24e and 24f, the pilot valves 25a,
25b, 25c, 25d, 25e and 25f being connected to both ends of the pressure
compensated flow-control valves 12, 15 and 16.

[0148]As shown in FIGS. 9 and 10, the electric control levers 22d, 22e and
22f are manipulable to a range approximately 110% (kickdown range)
relative to stroke range of normal control lever (100%) in the same
manner as the control levers 22a, 22b and 22c used in the first
embodiment. When the operation stroke of the control lever 22 exceeds
100%, an operation feeling is given where the lever does not move without
applying further greater control force.

[0149]Further, when the control levers 22d, 22e and 22f are manipulated,
the output signal proportionally changes from stroke 0% to stroke 110% of
the kickdown range. The controller 23 recognizes that the control levers
22d, 22e and 22f have reached to the kickdown range when the output
signal received from the control levers 22d, 22e and 22f exceeds a
predetermined value (SL).

[0150]The same effects and advantages as the first embodiment can be
expected in the second embodiment.

Third Embodiment

[0151]FIG. 11 shows a control system circuit of an electric excavator
according to third embodiment of the invention. The control system
circuit of the present embodiment differs from the hydraulic control
circuit of the first embodiment in the following.

[0152]In the second embodiment, instead of the swing actuator (swing
hydraulic motor 2), the pressure compensated flow-control valve 15 of the
swing hydraulic motor 2, the boom actuator (boom cylinder 6), the
pressure compensated flow-control valve 12 of the boom cylinder 6, the
arm actuator (arm cylinder 7) and the pressure compensated flow-control
valve 16 of the arm cylinder 7, a swing actuator (swing electric motor
102), an inverter 115 of the swing electric motor 102, a boom actuator
(boom cylinder device 106), an inverter 112 of the boom cylinder device
106, an arm actuator (arm cylinder device 107) and an inverter 116 of the
arm cylinder device 107 are provided. A battery 110 and a capacitor
(electrical condenser) 113 that is charged by the battery 110 are
connected to the inverters 115, 112 and 116 via a power controller 120.

[0153]In this connection, a control signal from the controller 23 is
transmitted to the respective inverters 115, 112 and 116, the power
controller 120, the battery 110 and the capacitor 113 via the signal
circuits 24a, 24c, 24e, 24g, 24h and 24i.

[0154]When the electric control levers 22d, 22e and 22f are constructed by
the same levers as those used in the second embodiment, the same effects
and advantages as the first embodiment are expected in the third
embodiment.

[0155]Further, since the total output is controlled by the command from
the controller 23 to the inverters 12, 15 and 16 and the power controller
120, the output (110%) when the power-up mode is set on is also increased
by the command from the controller 23 to the inverters 12, 15 and 16 and
the power controller 120.

[0156]It should be readily understood that the present embodiment is
applicable to a combination of hydraulic actuator and electric actuator
(so-called hybrid excavator).

[0157]Incidentally, the scope of the present invention is not limited to
the above-described embodiment, but includes modifications and
improvements as long as an object of the present invention can be
achieved.

[0158]For instance, though the operation feeling (notifying unit) provided
to the control lever is designed so that, when the control lever reaches
to the kickdown range, control force greater than previous control force
is required for moving the control lever, other arrangement is possible.
On the contrary, the control lever may be designed so that, when the
control lever reaches to the kickdown range, the control lever can be
moved with a force smaller than the previous force. Alternatively, a
notifying unit 80 as shown in FIG. 12 may be used.

[0159]The notifying unit 80 shown in FIG. 12 includes: a sector-shaped
rotary plate 81 provided at a rotation support point of the control lever
22; two slide bars 83A and 83B that are in contact with oblique sides of
the rotary plate 81 and are advanced and retracted in accordance with the
rotation of the rotary plate 81, the slide bars including notched grooves
82A and 82B arranged in the axial direction sandwiching intermediary
projections 87A and 87B; springs 84A and 84B that biases the slide bars
83A and 83B so that the respective ends of the slide bars 83A and 83B
touch the oblique sides of the rotary plate 81; balls 85A and 85B
slidably provided on the sides of the slide bars 83A and 83B; and springs
86A and 86B that press and bias the balls 85A and 85B in a direction to
touch the sides of the slide bars 83A and 83B.

[0160]According to the above arrangement, the rotary plate 81 is rotated
in accordance with the rotation of the control lever 22. Then, either one
of the slide bars 83A and 83B are slid downward (in the figure) in
accordance with the rotary direction. When one of the projections 87A and
87B of either one of the slide bars 83A and 83B reaches to the position
of the balls 85A and 85B, the projection 87A or 87B pushes the balls 85A
or 85B against the springs 86A or 86B, so that the force for downwardly
(in the figure) sliding the slide bars 83A and 83B is momentarily
changed. Accordingly, an operator who manipulates the control lever 22
feels the change in the control force of the control lever 22 and can
recognize that the control lever has reached to the kickdown range.

[0161]Further, the movement of the control lever may not be felt by the
control force but by visual sense, auditory sense, touch and the like.
Specifically, arrival of the control lever to the kickdown range may be
notified on a display device using a character or a picture, by sound
from a speaker, or vibration of the control lever.

[0162]Further, the detecting means for detecting the arrival of the
control lever to the proximity of the control range may not be a limit
switch as in the above embodiments, but other arrangement is possible.
For instance, an electric contact point that is electrically in contact
with the control lever may be provided adjacent to the control range of
the control lever and the arrival is detected when the electric contact
point touches the control lever. Alternatively, an optical sensor is
provided adjacent to the control range of the control lever and the
arrival may be detected when the control lever blocks the optical sensor.

INDUSTRIAL APPLICABILITY

[0163]The present invention is applicable to a hydraulic excavator as well
as other construction machines in general.